1. Field of the Invention
The present invention relates to automotive electronics, and more particularly to tire pressure monitoring.
2. Discussion of Related Art
Proper tire pressure in automotive tires is important for ensuring safe handling, maintaining gas mileage, reducing tread wear, and preventing tire blowouts. Under-inflated or over-inflated tires can negatively affect the handling of a vehicle, resulting in under-steer, over-steer, and/or an increased tendency to hydroplane in wet conditions.
Under-inflation is a more common problem as tire pressure typically decreases over time. Under-inflated tires increase rolling resistance, decreasing gas mileage and increasing tire wear. Further, under-inflated tires flex greatly as they roll, the flexing generates heat as different layers of the tire rub against one another. The heat can reach temperatures beyond the operating parameters of the tire causing catastrophic tire failure.
These problems are exacerbated by the increasing use of “run-flat” tires. A run-flat tire enables a vehicle to travel an extended distance after a significant loss of air pressure within the tire through the use of, for example, stiff tire sidewalls. Thus, even a significant loss of air pressure within the tire may go unrecognized by a vehicle operator because the loss of air pressure may cause only a small deflection of the sidewall. Because the sidewall is capable of maintaining the shape of an under-inflated tire, the handling characteristics of the vehicle during typical operation may not be affected. However, the under-inflation can seriously affect handling in an emergency situation where the stresses placed on the tire can be much greater than during typical operation. For these and other reasons, proper air pressure is important to the safe and efficient operation of a motor vehicle.
Since air pressure is typically overlooked as part of vehicle maintenance, systems have been developed to inform vehicle operators of low-pressure situations. These systems are typically sold as part of a factory installed package with new vehicles.
Various tire pressure monitoring systems have been developed to provide information to a vehicle operator, for example, a tire pressure monitoring system that detects when air pressure within a tire drops below a predetermined threshold pressure value.
Typically, a tire pressure monitoring system comprises a tire pressure sensor, a tire pressure signal transmitter, a tire pressure signal receiver, and an indicator or display located on a vehicle instrument panel. The tire pressure sensor and the tire pressure signal transmitter are located inside the tire. The tire pressure sensor may transmit radio frequency signals through the transmitter that are received by an antenna located in the vehicle.
Tire pressure sensors have been developed with various designs. For example, tire pressure sensors and transmitters have been attached to air valves. Another system utilizes a strap to attach the sensor and transmitter to a rim.
While the tire pressure monitoring systems are useful to vehicle operators, the systems are typically standalone systems having dedicated wiring and interfaces.
Therefore, a need exists for an integrated monitoring system for monitoring tire air pressure and vehicle security.